I'm generally pretty strait-laced on these piracy ethics questions, but I would point out a few things about #4:

a.) unless the Rhino student discount specifically prohibits the student from reselling it to you at his cost, it's hard to argue that it's even unethical, much less illegal. He's a student, he uses his discount. He has paid for the software and is entitled to dispose of it as he wishes.

b.) I don't see how whether you're going to use the software professionally or not affects the ethics of the sale at all. Do you hurt Rhino in some way by using the product professionally as opposed to using for a hobby? Of course not. On the contrary, your professional use is likely to provide free advertising for Rhino.

c.) You don't ask whether the student discount is an ethical policy in itself. Actually, it's just a disguised version of the sort of kickback pricing that is considered unethical and illegal in some sorts of anti-trust law. (Though not by me.) Yeah, if you look at it from one direction, it's a public-spirited way of putting the software into the hands of students who don't have much money. But if you look at it from the other direction -- just as accurately -- it's a way of getting as much as you can from poor students while charging more well-to-do people a surplus price. I personally have nothing against charging what the market will bear, but don't tell me this is a morally or ethically elevated policy; it isn't.

d.) If there's no way you would pay the full price, Rhino is getting money they wouldn't otherwise have gotten from you. You in turn must do some little favor for the student to secure his participation, so if Rhino's policy really was motivated by a desire to help students, that too has been accomplished (a little).

e.) And in fact, to generalize the argument from c.) companies who set up these discounts don't really care if the students "cheat" because in fact, that's part of their profit-maximizing scheme. If the student doesn't feel like using the discount for himself, it's better for the company if he employs it for someone else who wasn't going to pay the surplus price anyway. Of course, you have to protect the surplus price by only offering so many discount slots; the student can only buy one copy, for instance. Every big company I've ever worked for that offered an employee's discount understood that we employees would broker deals for our family and friends; they understood that by telling our friends or family we had the discount we were in effect running a sale for the company, and an effective one; they just set a numerical limit on how much we could buy so they could maintain an everyday non-sale price as well.

So, the "students only" thing is really just a fiction employed by the company, one of many marketing tools like volume discounts, group discounts, seasonal sales, etc.

If a special discount actually priced the software below cost, that would be something else again. But of course, with software, that possibility doesn't come up -- is indeed laughable.

Don't get me wrong. I'm not one of those people who goes on and on about how all high prices are theft, blah blah blah; the software business is no bed of roses, some of the best providers don't break even, and I'm always happy to pay the non-pirate price for good programs. (If they're really overpriced, like Photoshop, some competitor will provide nearly all the same functionality at a more reasonable cost; or I will eventually find an Adobe discount that applies to me.) But scooping the student discount price, or your sister's employee discount price, is no more unethical than taking the upgrade discount price. The company has alotted all these price slots in its marketing plan, makes its profit, and no one is harmed.